1. Field of the Invention
The present invention relates to guardrail structure and more particularly to a metal tube structure for guardrail with improved characteristics.
2. Description of Related Art
A conventional guardrail comprises two parallel metal tubes with a protective board mounted in between. Such metal tube 100 is shown in FIGS. 14 and 15 and is formed by bending an elongate strip of steel sheet material 90 into a hoop, pressing from underside to form an elongate groove 92 having a section of inverted U and a top abutment plate 91, and welding the hoop along a weld line 93 to finish the product.
However, the prior art suffered from several disadvantages. For example, an additional polishing step is required to smooth the weld line 93. Further, the metal tube 100 may be not straight after the welding. Furthermore, the manufacturing process is time consuming, not economical. Also, both welding and polishing are risky jobs and may contaminate the environment.
Thus, it is desirable to provide an improved metal tube structure for guardrail in order to overcome the above drawbacks of the prior art.